Reciprocal latching ferrite waveguide phase shifter having waveguide stubs energized in phase quadrature

ABSTRACT

A waveguide phase shifter of the loaded line type using latching ferrite material as the active element. The active ferrite material is fabricated in the shape of thin and low-volume toroids which are disposed in pairs in waveguide stubs that are coupled to a main waveguide by coupling slots formed therein. Means are provided for alternatively energizing the toroids into either a symmetrical state or an antisymmetrical state. The changes in impedance and phase constants between these two different states produce susceptance changes across the coupling slots thereby effecting corresponding changes in the phase of microwave signals propagated over the main waveguide. This phase shift of the signals is reciprocal.

United States Patent John Ineson Smith Morris Township, Morris County, NJ. 45,695

June 12, 1970 Nov. 23, 1971 Bell Telephone Laboratories, Incorporated Murray Hill, Berkeley Heights, NJ

[ 72] Inventor [21 Appl. No. [22] Filed [45 Patented [73] Assignee [54] RECIPROCAL LATCHING FERRITE WAVEGUIDE PHASE SHIFI'ER HAVING WAVEGUIDE STUBS ENERGIZED IN PHASE QUADRATURE 3,384,841 5/1968 Di Piazza 333/31 Primary Examiner-Herman Karl Saalbach Assistant Examiner-Paul L. Gensler Attorneys-R. .1. Guenther and William L. Keefauver ABSTRACT: A waveguide phase shifter of the loaded line type using latching ferrite material as the active element. The active ferrite material is fabricated in the shape of thin and low-volume toroids which are disposed in pairs in waveguide stubs that are coupled to a main waveguide by coupling slots formed therein. Means are provided for alternatively energizing the toroids into either a symmetrical state or an antisymmetrical state. The changes in impedance and phase constants between these two different states produce susceptance changes across the coupling slots thereby effecting corresponding changes in the phase of microwave signals propagated over the main waveguide. This phase shift of the signals is reciprocal.

PATENTED-N 23 3.623.149

SHEET 2 OF 2 FIG. 3

been nonreciprocal. Recently,

RECIPROCAL LATCHING FERRITE WAVEGUIDE PHASE SHIF'IER HAVING WAVEGUIDE STUBS ENERGIZED IN PHASE QUADRATURE GOVERNMENT CONTRACT BACKGROUND OF THE INVENTION This invention relates to waveguide phase shifters and, more particularly, to reciprocal waveguide phase shifters of the loaded line type using latching ferrite material as the active element.

Heretofore, the usual type of waveguide phase shifter using latching ferrite material as the active element has, in general, a prior art waveguide phase shifter, which is disclosed in U.S. Pat. No. 3,425,003 issued Jan. 28, 1968, to M. C. Mohr, has obtained reciprocal phase shifts by employing massive latching ferrite elements. In this prior art phase shifter, the ferrite elements are positioned within the main waveguide that is employed for the propagation of microwave signals. This construction does not offer the versatility of a loaded line phase shifter wherein a small change in the propagation parameters of ferrite material in associated stub lines is transformed by the stubs to a susceptance change in the main line. Furthermore, ferrite phase shifters, such as that shown in the patent to Mohr, the ferrite elements have a relatively massive construction which requires relatively large magnetizing currents and this results in increasing the time needed to switch from one binary remanent magnetization state to another.

SUMMARY OF THE INVENTION The present invention is designed to provide a waveguide phase shifter with several improvements over the abovedescribed phase shifter. This is accomplished by constructing an improved reciprocal waveguide phase shifter of the loaded line type using latching ferrite material as. the active element.

A The active ferrite material is fabricated in the shape of thin and low volume toroids which are disposed in pairs in waveguide stubs that are coupled to a main waveguide by coupling slots formed therein. Means are provided for altematively energizing the toroids into either a symmetrical state or an antisymmetrical state. The changes in impedance and phase constants between these two different states produce susceptance changes across the coupling slots thereby efiecting corresponding changes in the phase of microwave signals propagated over the main waveguide. This phase shift of the signals is reciprocal.

Matching over a band of signal frequencies is achieved by employing two or more waveguide stubs properly spaced,

usually approximately a quarter wavelength apart at the operating frequency, along the main waveguide. A wide range of waveguide and stub impedance values and stub length are available as design parameters to complement the particular power and circuit capabilities of the ferrite toroids. The dimensions of the toroids provide additional variables that are useful in obtaining low variation of differential phase over a frequency band.

Since each of the toroids uses a low volume of ferrite material, only minimal magnetizing currents are required to switch them from one state of remanence to another. This serves to maximize the rapidity of the switching action of this phase shifter.

BRIEF DESCRIPTION OF THE DRAWING The features of this invention are more fully discussed hereinafter in connection with the following detailed description of the drawing in which:

FIG. 1 is a perspective view, partly in section, of a waveguide phase shifter of the loaded line type constructed in accordance with this invention;

in the prior art latching FIG. 2 is a schematic diagram of the circuits and switching means used for applying magnetizing currents to the ferrite toroids in the stub waveguides;

FIG. 3 is a schematic diagram illustrating one of the binary remanent magnetization states in one of the pairs of ferrite toroids; and

FIG. 4 is a schematic diagram somewhat similar to that of FIG. 3 but representing the other binary remanent magnetization state in the same pair of ferrite toroids.

DETAILEDDESCRIPT ION A specific exemplary embodiment of the invention is represented in FIG. 1 as comprising a section of a main waveguide 1 having a width that is. approximately twice as large as its height. The waveguide 1- has a signal input 2 coupled to one end thereof for the propagation thereover of microwave signals to-a signal output 3 coupled to the other end thereof. Two waveguide stubs 4 and 5, which are substantially identical, are attached to the main waveguide l and are spaced apart by a distance which is approximately equal to a quarter of a wavelength at the operating frequency.

As is indicated in FIG. I, a rectangular coupling slot 6 is formed in the main. waveguide 1 under the stub waveguide 4 for supplying microwave signaling energy thereto. The length of the slot 6 does not exceed the width of the main waveguide I. It is tobe understood that a similar coupling slot is provided for coupling microwave signaling energy to the other stub waveguide 5. Since, in this exemplary embodiment of the invention, the width of each of the coupling slots 9 is so constructed as to be less than one-half the height of the main waveguide 1, any shunt discontinuities thatmight be produced by the slots will be negligible.

In FIG. 1, a portion of the sidewalls and the terminating, or shorting, plate 10 of the upper stub waveguide 4 have been broken away for the purpose of showing that it is provided at. the end thereof with a terminating reactance comprising its shorting plate 10 and a pair of thin, or low volume, toroids 7 and 8 composed of latching ferrite material. Each of the toroids 7 and 8v has means defining a central opening formed therein which is filled with a suitable dielectric material 9, such as Teflon. The toroids 7 and 8 are spaced apart from each other and the intervening space, as well as the remaining space. inside the stub waveguide 4, is filled with the dielectric material 9 which functions to support and retain the toroids 7 and 8. in their spaced positions inside the stub waveguides 4 and 5. A similar pair of ferrite toroids are correspondingly disposed within dielectric material inside the other stub waveguide 5. Each ferrite toroid in each pair is so positioned that its central opening faces toward its respectively associated coupling slot in the main waveguide I.

As was statedabove, the two pairs of toroids are composed of latching ferrite material. These pairs of toroids are adapted to have two alternative states of remanent magnetization one being a symmetrical, or even, state and the other being an antisymmetrical, or odd, state. These two alternative states can be producedv selectively inside the stub waveguides 4 and 5 by changing the direction in which a magnetizing current flows through magnetizing turns that are disposed around the toroids.

One method for accomplishing this is shown schematically in FIG. 2 wherein the first pair of ferrite toroids 7 and 8 is shown to be positioned above the other pair of ferrite toroids l1 and 12. Each of these pairs of toroids is supplied with magnetizing current from respectively associated sources of electric current, such as the batteries 13 and 14, which are substantially identical. The direction of the flow of this magnetizing current is adapted to be changed by means of identical reversing switches 15 and 16. The switches l5 and 16 are connected by a common operating arm, or instrumentality, 17 so that both switches are moved from one position to another simultaneously. If desired, this operation of the switches 15 and 16 can be performed in time sequence.

Considering, for example, the upper pair of toroids 7 and 8, it can be seen that, when the switch 15 is in the position shown in FIG. 2, magnetizing current will flow from the upper side of the voltage source 13 to the lower arm of the switch 15, then over a cross-connector to the upper portion of a lead 18, through one turn of the lead 18 around the toroid 7, then along the lower section of the lead 18, over the other crossconnector to the upper arm of the switch 15, then over the upper portion of a lead 19, through one turn of the lead 19 around the toroid 8, and then back along the lower portion of the lead 19 to the other side of the voltage source 13. This flow of the magnetizing energy through the turns around the toroids 7 and 8 in the stub waveguide 4 will produce one state of magnetization therein.

At this time magnetizing current from the battery 14 will fiow through the leads 21 and 22 in a similar manner and will produce the same state of magnetization in the other pair of toroids 11 and 12 inside the other stub waveguide 5. lt should be noted that the dielectric material 9 also functions to support the turns of the electrically conductive leads 18, 19, 21, and 22 inside the stub waveguides 4 and 5.

The opposite state of magnetization can be produced alternatively in the toroids 7 and 8 by moving the operating arm or instrumentality, 17 in such a manner as to move the arms of the switches 15 and 16 simultaneously to engage their other switch contacts. Now, magnetizing energy from the source 13 will flow over the lower arm of the switch 15, along the lower portion of the lead 18, through the turn around the toroid 7 but in a direction opposite to that described above, over the upper portion of the lead 18, over the upper arm of the switch 15 to the upper portion of the lead 19, through the turn around the toroid 8, and then back along the lower portion of the lead 19 to the other side of the voltage source 13. As this magnetizing energy now flows through the toroid 7 in a direction opposite to that previously described, the toroid 7 will now be magnetized in its other state.

Since, at this time, the arms of the switch 16 are also moved by the operating bar 17 to engage their other switch contacts, this opposite state of magnetization will also be produced in a similar manner in the toroid 11 of the other pair. Thus, the batteries 13 and 14, the switches 15 and 16, and the leads 18, 19, 21 and 22 comprise magnetizing means for providing magnetizing current to the stub waveguides 4 and for establishing two alternative states of magnetization therein.

The first of these alternative states of magnetization is represented in FIG. 3 by the four arrows drawn in the toroids 7 and 8. This represents the antisymmetrical, or odd, state of magnetization which occurs inside the stub waveguide 4 when the magnetizing energy flows through the lead 18 in the direction indicated by the arrows attached thereto.

The second state of magnetization is represented by the four arrows drawn in the toroids 7 and 8 shown in FIG. 4. Since the magnetizing energy is now assumed to be flowing through the lead 18 in the direction indicated by the arrows attached thereto and since this direction is the opposite of that previously assumed, the direction of the arrows in the toroid 7 will now be reversed by the arrows in the toroid 8 will have the same direction as is shown in FIG. 3. Thus, FIG. 4 represents the symmetrical, or even, state of magnetization that occurs alternatively inside the stub waveguide 4.

When microwave signaling energy is propagated past the coupling slots in the main waveguide 1, its phase can be changed by operating control means, comprising the operating instrumentality 17, for changing the reactances of the pairs of toroids inside the stub waveguides 4 and 5 by changing the the positions of the arms of the switching means constituted by the reversing switches and 16. The operation of the switches 15 and 16 will function to switch alternatively the latching ferrite toroids into either a symmetrical state of magnetization or an antisymmetrical state. This will produce a corresponding change in the terminating impedance presented by each pair of toroids to their respectively associated stub waveguides 4 and 5. These impedance changes are transformed by the length of the stubs 4 and 5 into changes in the input susceptance presented by the stub waveguides 4 and 5 to their respectively associated coupling slots 6.

The series susceptance across each of the coupling slots 6 comprises a fixed part and a variable part. The fixed part has a magnitude somewhat less than unity when it is normalized to the admittance of the main waveguide 1. The variable part is that which is produced by the switching of the ferrite toroids from one state to another. Due to the phase constant and impedance changes between these two different states of magnetization, phase shifts of the microwave signaling energy transmitted through the main waveguide l are obtained. These phase shifts of the signaling energy are reciprocal.

As was stated above, an advantage derived from employing a loaded line type of construction is that it provides a wide range of line and stub impedance values and stub length for use as design parameters to complement the particular power and circuit capabilities of the latching ferrite toroids. In addition, the dimensions of the ferrite toroids within the stub waveguides provide further variables that are useful in obtaining low variation of differential phase over a frequency band.

A most important consideration concerning the operation of ferrite phase shifters is that, when a large volume of ferrite material is required for producing a given phase shift, it is necessary to use correspondingly large magnetomotive forces and this results in increasing the time required to switch from one state of magnetization to the other state. Conversely, when only a relatively small volume of ferrite material is needed to produce the desired phase shift, then only relatively small magnetomotive forces are required and the necessary magnetization currents are correspondingly small thereby effecting a reduction in the time needed to switch from one magnetization state to another state.

Accordingly, it should be noted that, in the present invention, since each of the ferrite toroids is thin and uses only a low volume of the ferrite material, only minimal magnetizing currents are required to switch them from one state of magnetization to another.

In other words, the ferrite loaded stub waveguides 4 and S constitute maximizing means for maximizing the permissible rapidity of the alternative switching action performed by the switching means 15, 16, and 17. In addition, the abovedescribed thin and low volume construction of the ferrite toroids 7, 8, l1, and 12 constitutes minimizing means for minimizing the magnitude of the magnetizing current required to produce the desired phase shifts of the microwave signals. Therefore, the rapidity of the switching action of the phase shifter of this invention is maximized to an extent that has not heretofore been obtainable.

What is claimed is:

1. A loaded line ferrite phase shifter adapted for shifting the phase of microwave signals propagated over a main waveguide and comprising:

at least two stub waveguides coupled to said main waveguide in such a manner as to be energized in phase quadrature by said microwave signals, said stub waveguides having terminating reactances at the ends thereof adapted to be transformed by said stub waveguides into input susceptances which are presented to said microwave signals for imposing a phase shift thereon when propagated past said stub waveguides,

control means adapted for changing said phase shift by changing said reactances,

said control means including magnetizing means adapted for providing magnetizing current to each of said stub waveguides for establishing a state of magnetization therein,

switching means adapted for alternatively switching said state of magnetization in each of said stub waveguides from one state of magnetization to a different state of magnetization,

and maximizing means for maximizing the rapidity of said alternative switching action of said switching means,

said maximizing means comprising minimizing means for minimizing the required magnitude of said magnetizing currents, said minimizing means comprising at least four members composed of ferrite material and grouped in two pairs, and adapted to be magnetized by said magnetizing means each of said ferrite members being fabricated in the shape of a thin and low volume toroid,

and supporting means for supporting one pair of said ferrite toroids inside one of said stub waveguides and for supporting the other pair of said ferrite toroids inside the other of said stub waveguides.

2. A loaded line ferrite phase shifter in accordance with claim 1 wherein said state of magnetization in each of said stub waveguides is localized in the respectively associated pair of thin toroids supported therein,

and wherein said one state of magnetization in each of said stub waveguides is constituted by a symmetrical state of magnetization of the respectively associated pair of thin ferrite toroids supported therein,

and wherein said different state of magnetization in each of said stub waveguides is constituted by an antisymmetrical state of magnetization of the respectively associated pair of thin ferrite toroids supported therein. 3. A loaded line ferrite phase shifter in accordance with claim 1 wherein said main waveguide has means defining a plurality of slots formed therein with each of said slots being disposed under a respectively different one of said stub waveguides for supplying said microwave signals thereto,

wherein each of said thin ferrite toroids in said stub waveguides has means defining a central opening therein,

and wherein said supporting means is adapted for supporting each of said thin ferrite toroids in such a manner that its central opening faces toward a respectively associated one of said slots formed in said main waveguide.

4. A loaded line ferrite phase shifter in accordance with claim 2 wherein said main waveguide has a width that is approximately twice as large as its height,

and wherein each of said slots formed in said main waveguide has a rectangular shape with a length not in excess of the width of said main waveguide and with a width which is less than one-half the height of said main waveguide.

5. A loaded line ferrite phase shifter in accordance with claim 2 wherein said magnetizing means comprise a plurality of electrically conductive leads each being disposed with at least one turn thereof passing through the central opening in a respectively different one of said thin ferrite toroids,

each of said leads being connected to a source of magnetizing current for applying said magnetizing current to its respectively associated ferrite toroid,

wherein said switching means comprise means for directing the flow of said magnetizing current along said conductive leads in such a direction as to produce a symmetrical state of magnetization in both of said pairs of ferrite toroids in said stub waveguides,

and wherein said switching means further include means for alternatively reversing the direction of the flow of said magnetizing current along two of said conductive leads for producing an antisymmetrical state of magnetization in both of said pairs of ferrite toroids in said stub waveguides.

6. A loaded line ferrite phase shifter in accordance with claim 5 wherein said two conductive leads include one lead having at least one turn passing through the central opening of one ferrite toroid in the pair of toroids in one of said stub waveguides,

and wherein said two conductive leads further include one lead having at least one turn passing through the central opening of one ferrite toroid in the pair of toroids in the other of said stub waveguides.

7. A loaded line ferrite phase shifter adapted for shifting the phase of microwave signals propagated over a main waveguide and comprising:

at least two stub waveguides coupled to said main waveguide in such a manner as to be energized in phase quadrature by said microwave signals,

phase shifting means for producing a change in the susceptance presented by said stub waveguides to said main waveguide whereby the phase of said microwave signals propagated over said main waveguide is changed, said phase shifting means comprising a first pair of latching ferrite toroids positioned within said first stub waveguide,

a second pair of latching ferrite toroids positioned within said second stub waveguide,

each of said pairs of toroids having a symmetrical state of magnetization and also alternatively having an antisymmetrical state of magnetization,

first electric conduction means extending through said first pair of toroids,

second electric conduction means extending through said second pair of toroids,

means for energizing said first and second electric conduction means for latching both of said pairs of ferrite toroids in said stub waveguides into said symmetrical state of magnetization,

and means for alternatively energizing said first and second electric conduction means for latching both of said pair of toroids in said stub waveguides into said antisymmetrical state of magnetization.

t t I? t t 

1. A loaded line ferrite phase shifter adapted for shifting the phase of microwave signals propagated over a main waveguide and comprising: at least two stub waveguides coupled to said main waveguide in such a manner as to be energized in phase quadrature by said microwave signals, said stub waveguides having terminating reactances at the ends thereof adapted to be transformed by said stub waveguides into input susceptances which are presented to said microwave signals for imposing a phase shift thereon when propagated past said stub waveguides, control means adapted for changing said phase shift by changing said reactances, said control means including magnetizing means adapted for providing magnetizing current to each of said stub waveguides for establishing a state of magnetization therein, switching means adapted for alternatively switching said state of magnetization in each of said stub waveguides from one state of magnetization to a different state of magnetization, and maximizing means for maximizing the rapidity of said alternative switching action of said switching means, said maximizing means comprising minimizing means for minimizing the required magnitude of said magnetizing currents, said minimizing means comprising at least four members composed of ferrite material and grouped in two pairs, and adapted to be magnetized by said magnetizing means each of said ferrite members being fabricated in the shape of a thin and low volume toroid, and supporting means for supporting one pair of said ferrite toroids inside one of said stub waveguides and for supporting the other pair of said ferrite toroids inside the other of said stub waveguides.
 2. A loaded line ferrite phase shifter in accordance with claim 1 wherein said state of magnetization in each of said stub waveguides is localized in the respectively associated pair of thin toroids supported therein, and wherein said one state of magnetization in each of said stub waveguides is constituted by a symmetrical state of magnetization of the respectively associated pair of thin ferrite toroids supported therein, and wherein said different state of magnetization in each of said stub waveguides is constituted by an antisymmetrical state of magnetization of the respectively associated pair of thin ferrite toroids supported therein.
 3. A loaded line ferrite phase shifter in accordance with claim 1 wherein said main waveguide has means defining a plurality of slots formed therein with each of said slots being disposed under a respectively different one of said stub waveguides for supplying said microwave signals thereto, wherein each of said thin ferrite toroids in said stub waveguides has means defining a central opening therein, and wherein said supporting means is adapted for supporting each of said thin ferrite toroids in such a manner that its central opening faces toward a respectively associated one of said slots formed in said main waveguide.
 4. A loaded line ferrite phase shifter in accordance with claim 2 wherein said main waveguide has a width that is approximately twice as large as its height, and wherein each of said slots formed in said main waveguide has a rectangular shape with a length not in excess of the width of said main waveguide and with a width which is less than one-half the height of said main waveguide.
 5. A loaded line ferrite phase shifter in accordance with claim 2 wherein said magnetizing means comprise a plurality of electrically conductive leads each being disposed with at least one turn thereof passing through the central opening in a respectively different one of said thin ferrite toroids, each of said leads beiNg connected to a source of magnetizing current for applying said magnetizing current to its respectively associated ferrite toroid, wherein said switching means comprise means for directing the flow of said magnetizing current along said conductive leads in such a direction as to produce a symmetrical state of magnetization in both of said pairs of ferrite toroids in said stub waveguides, and wherein said switching means further include means for alternatively reversing the direction of the flow of said magnetizing current along two of said conductive leads for producing an antisymmetrical state of magnetization in both of said pairs of ferrite toroids in said stub waveguides.
 6. A loaded line ferrite phase shifter in accordance with claim 5 wherein said two conductive leads include one lead having at least one turn passing through the central opening of one ferrite toroid in the pair of toroids in one of said stub waveguides, and wherein said two conductive leads further include one lead having at least one turn passing through the central opening of one ferrite toroid in the pair of toroids in the other of said stub waveguides.
 7. A loaded line ferrite phase shifter adapted for shifting the phase of microwave signals propagated over a main waveguide and comprising: at least two stub waveguides coupled to said main waveguide in such a manner as to be energized in phase quadrature by said microwave signals, phase shifting means for producing a change in the susceptance presented by said stub waveguides to said main waveguide whereby the phase of said microwave signals propagated over said main waveguide is changed, said phase shifting means comprising a first pair of latching ferrite toroids positioned within said first stub waveguide, a second pair of latching ferrite toroids positioned within said second stub waveguide, each of said pairs of toroids having a symmetrical state of magnetization and also alternatively having an antisymmetrical state of magnetization, first electric conduction means extending through said first pair of toroids, second electric conduction means extending through said second pair of toroids, means for energizing said first and second electric conduction means for latching both of said pairs of ferrite toroids in said stub waveguides into said symmetrical state of magnetization, and means for alternatively energizing said first and second electric conduction means for latching both of said pair of toroids in said stub waveguides into said antisymmetrical state of magnetization. 